This invention relates to a combination fertilizer composition and to a process for treating vegetation with the fertilizer composition which enhances the effect of the fertilizer, extends its period of desirable response and reduces the amount of fertilizer necessary to maintain quality vegetation.
Ideal maintenance of high quality turf results when nitrogen fertilizer applications roughly coincide with the plant's nutrient demand. This balance of nutrient input and outgo has never been achieved with either quick release soluble fertilizers or with more slowly released coated or less soluble fertilizers.
Following the application of soluble fertilizers, the plant is provided an excess amount of nutrients. This is evidenced as surge growth which leads to greater labor in the culture of turfgrasses in the form of more frequent mowing and greater clipping removal. Because the plant cannot accommodate all the nutrient provided in soluble formulations, nutrients are prone to be lost to the environment via surface runoff and/or leaching. Because soluble fertilizers are not efficiently used, such products must be applied frequently and at fairly high application rates (43.6-78.4 lbs. nitrogen per acre, four to five times/year).
Slow release nitrogen fertilizers have been developed to better match nutrient availability with demand by the plant. Although certain of these slow-release nitrogen sources do provide extended residual activity, problems still remain. Certain sources (ureaform, isobutylidene diurea) are slow in providing initial greening. This encourages repeat application by the impatient homeowner. Further, these sources may not readily break down so that large quantities of nitrogen accumulate in the soil. Some slow release sources (sulfur coated urea) tend to be inefficient in that up to 30% of the nitrogen is released so slowly so as to be nutritionally insignificant. Thus, the commonly used slow release fertilizers do not optimally match plant nutrient need with availability. This results in the need for high application rates (87 to 130 lbs. nitrogen per acre, two to three times per year).
With enhanced awareness of limited fertilizer supply, high cost and potential loss of nutrients to the environment, many homeowners as well as professional turfgrass managers are reducing fertilizer application, often at the sacrifice of turf quality. There are a number of adverse effects of inadequate fertilization. Grass stands thin which promotes runoff of nutrients and soil and the stands become vulnerable to invasion by weeds which must be controlled with pesticides. Further, the aesthetic benefit of well maintained turfgrass is of course lost.
Compounds which accelerate or retard the rate of growth of plants have been known for some time. Chemicals which retard or inhibit shoot and leaf elongation can be categorized by four modes of action: (1) inhibition of mitosis in the meristematic tissue which stops cell division and cell elongation (mitotic inhibitors), (2) reduction of cell elongation by inhibiting or retarding gibberellin synthesis, a plant hormone necessary for cell elongation (gibberellin synthesis inhibitors), (3) regulating auxin activity and transport (auxin modifiers) and (4) killing terminal buds thus reducing apical dominance (chemical bud pinchers). All four modes of action are effective in higher plants; however the latter two are only moderately effective or totally ineffective on turfgrasses. Mitotic inhibitors include such compounds as chlorflurenol, mefluidide, and maleic hydrazide. Until very recently these were the only three growth regulators commercially available for use on turfgrasses. These compounds and their use as growth regulators are further discussed in "Plant Growth Regulating Chemicals", Louis G. Nickell, CRC Press, Vol. II (1983). Those which retard gibberellin synthesis include such compounds as paclobutrazol (PP-333) and flurprimidol (EL-500), discussed further below.
The combination of a plant growth regulator of the type which inhibits mitosis and a fertilizer was first reported in 1969 in McVey et al U.S. Pat. No. 3,462,257. The stated purpose of the combination was to improve turf color and quality while reducing turf growth. However, the combination product disclosed in the McVey et al patent possesses a number of limitations which have effectively prevented its use. The plant growth regulator disclosed in the McVey et al patent, 6 azauracil and certain of its derivatives and salts, requires a usage level well above the level of tolerance of certain grass species. Moreover, recovery from inhibition with this combination product is rapid, resulting in surge growth and narrower blade widths, both undesirable in turf maintenance programs.
The compounds paclobutrazol [(2RS, 3RS)-1-(4chlorophenyl)-4, 4-dimethyl-2-(1,2,4-triazol-1-yl-)pentan-3-ol] and flurprimidol [.alpha.-(1-methylethyl)-.alpha.[4-(trifluoromethoxy)phenyl]-5-pyrimidine- methanol] have been reported relatively recently as plant growth regulators. Paclobutrazol and its use as a fungicide and plant growth regulator are disclosed in U.S. Pat. No. 4,243,405 which issued on Jan. 6, 1981. The patent discloses a broad range of rates of usage for the compounds as fungicides and plant growth regulators, of from 0.1 to 15 kg per hectare (0.089 to 13.38 pounds per acre), although it indicates that applications within this range may produce phytotoxic effects on certain plants. Its use as a plant growth regulator on a variety of plants including Lolium ryegrass is shown at 5000 parts per million which, based on a conservative calculation of 80 to 200 gallons per acre of water, resulted in about 2 to 9 pounds per acre of the growth regulating compound. The patent also states that at least 75% by weight of the final fertilizer granules can be fertilizer, and up to 25% can be growth regulating compound. Flurprimidol and its use as a herbicide, fungicide and plant growth regulator are disclosed in U.S. Pat. No. 4,002,628 which issued on Jan. 11, 1977. The patent discloses that internodal elongation of plants, including turf, is inhibited by treatment with the compounds there disclosed at rates of about 0.125 to about 5 pounds per acre.
Watschke (Agronomy Abstracts, 1982 page 146) discloses the application of nitrogen fertilizer to turf 7 weeks after treating with PP-333 and EL-500. Fertilizer was applied to overcome the injury associated with these growth regulators. The article reports an improvement in turf color following application of the fertilizer, but an associated reduction in the duration of chemical suppression.
Mefluidide (N-[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl]amino]-phenyl]acetamide) is a growth regulator which inhibits mitosis (cell division) and is recommended at 0.25 to 1.0 pound in 15 to 150 gallons of water per acre. Mefluidide's use as inhibitors for the growth of grass is the subject of U.S. Pat. No. 4,013,444 to Fridinger which shows a range of suggested uses as a growth regulator of from 0.15 to 2 pounds per acre. Mefluidide has been used alone or in combination with PP-333 by a number of researchers. Rates range from 0.125 up to 0.375 pounds per acre of mefluidide when used alone (Watschke NEWSS, Vol. 35, 1981, pages 322-329, Jagschitz NEWSS, Vol. 36, 1982, pages 334-335 and Bingham et al, Plant Protection Results, VPI 1981, pages 49-54). In combination with PP-333 (0.25-2.0 pounds per acre) mefluidide has been evaluated at 0.032 up to 0.250 pounds per acre (Shearman, University of Nebraska Project PGR-N82-1, 1982, Sawyer et al NEWSS, Vol. 37, 1983, pages 372-375 and Jagschitz et al NEWSS, Vol. 37, 1983, pages 58-64 and Bingham et al, Plant Protection Results, VPI 1981 pages 49-54). The addition of mefluidide at the above rates in combination with PP-333 (0.25-2.0 pounds per acre level) had little or no effect on enhancing PP-333 activity. In contrast, Jagschitz et al NEWSS, Vol. 37, 1983, pages 58-64, used mefluidide (0.08 up to 0.125 pounds per acre) in combination with PP-333 (0.25 up to 1.00 pounds per acre) and found that growth inhibition was enhanced by the addition of mefluidide regardless of PP-333 rate. However, the turf color was considered objectionable in the presence of all rates of mefluidide during the first 4 weeks following treatment. Bingham et al, Plant Protection Results, VPI 1981, pages 49-54 reported that single applications of 0.125 to 0.375 pounds per acre of mefluidide causes discoloration of bluegrass and Kentucky 31 fescue. In combination with PP-333, rates of 0.062 to 0.25 of mefluidide with 0.25 to 2.0 pounds of PP-333 per acre also caused varying degrees of discoloration. In addition, growth of Kentucky bluegrass with the combination of growth regulators was completely stopped for 4-6 weeks.